Ezekiel 3:20 (NKJV)
20 “Again, when a righteous man turns from his righteousness and
commits iniquity, and I lay a stumbling block before him, he shall
die; because you did not give him warning, he shall die in his sin,
and his righteousness which he has done shall not be remembered; but
his blood I will require at your hand.
Well, you'd better do something or God will require his blood at your hand.
As many as I love, I rebuke and chasten. Therefore be zealous and
If you sincerely love this friend of yours then you need to rebuke and chasten them in order to correct them in their ways.
We are given the instructions that we must approach and rebuke a brother in private. If he doesn't listen then take two or more brothers with you, if He still does not listen then rebuke him in front of the church.
If then he still does not listen then do not associate with such a person. Cast them out into the world and let God judge them for you have done what you need to do and their blood will not be on your hands.